Buggy code:
public class Uploader implements SynapsePersistable , SynapseWidgetPresenter , UploaderView . Presenter , ProgressingFileUploadHandler { public static final long OLD_BROWSER_MAX_SIZE = ( ( long ) ( ClientProperties . MB ) ) * 5 ; public static final String DEFAULT_EXTERNAL_S3_BANNER = "External<seq2seq4repair_space>S3<seq2seq4repair_space>Storage's<seq2seq4repair_space>banner<seq2seq4repair_space>has<seq2seq4repair_space>not<seq2seq4repair_space>set<seq2seq4repair_space>or<seq2seq4repair_space>is<seq2seq4repair_space>an<seq2seq4repair_space>empty<seq2seq4repair_space>string." ; private UploaderView view ; private HandlerManager handlerManager ; private Entity entity ; private String parentEntityId ; private String entityId ; private CallbackP < String > fileHandleIdCallback ; private SynapseClientAsync synapseClient ; private SynapseJSNIUtils synapseJsniUtils ; private GlobalApplicationState globalAppState ; private GWTWrapper gwt ; MultipartUploader multiPartUploader ; AuthenticationController authenticationController ; private String [ ] fileNames ; private int currIndex ; private NumberFormat percentFormat ; private boolean fileHasBeenUploaded = false ; private UploadType currentUploadType ; private String currentExternalUploadUrl ; private ClientLogger logger ; private Long storageLocationId ; @ Inject public Uploader ( UploaderView view , SynapseClientAsync synapseClient , SynapseJSNIUtils synapseJsniUtils , GWTWrapper gwt , AuthenticationController authenticationController , MultipartUploader multiPartUploader , GlobalApplicationState globalAppState , ClientLogger logger ) { } public Widget asWidget ( Entity entity ) { } public Widget asWidget ( String parentEntityId ) { } public Widget asWidget ( Entity entity , String parentEntityId , CallbackP < String > fileHandleIdCallback , boolean isEntity ) { } public void clearState ( ) { } @ Override public Widget asWidget ( ) { } public void uploadFiles ( ) { } public String [ ] getSelectedFileNames ( ) { } @ Override public String getSelectedFilesText ( ) { } @ Override public void handleUploads ( ) { } public void updateS3UploadBannerView ( String banner ) { } public void queryForUploadDestination ( ) { enableMultipleFileUploads ( ) ; storageLocationId = null ; if ( ( ( parentEntityId ) == null ) && ( ( entity ) == null ) ) { currentUploadType = UploadType . S3 ; view . showUploadingToSynapseStorage ( ) ; } else { String uploadDestinationsEntityId = ( ( parentEntityId ) != null ) ? parentEntityId : entity . getId ( ) ; synapseClient . getUploadDestinations ( uploadDestinationsEntityId , new com . google . gwt . user . client . rpc . AsyncCallback < java . util . List < UploadDestination > > ( ) { public void onSuccess ( java . util . List < UploadDestination > uploadDestinations ) { if ( ( uploadDestinations == null ) || ( uploadDestinations . isEmpty ( ) ) ) { currentUploadType = UploadType . S3 ; view . showUploadingToSynapseStorage ( ) ; } else if ( ( uploadDestinations . get ( 0 ) ) instanceof S3UploadDestination ) { currentUploadType = UploadType . S3 ; storageLocationId = uploadDestinations . get ( 0 ) . getStorageLocationId ( ) ; updateS3UploadBannerView ( uploadDestinations . get ( 0 ) . getBanner ( ) ) ; } else if ( ( uploadDestinations . get ( 0 ) ) instanceof ExternalUploadDestination ) { ExternalUploadDestination externalUploadDestination = ( ( ExternalUploadDestination ) ( uploadDestinations . get ( 0 ) ) ) ; storageLocationId = externalUploadDestination . getStorageLocationId ( ) ; currentUploadType = externalUploadDestination . getUploadType ( ) ; if ( ( currentUploadType ) == ( UploadType . SFTP ) ) { currentExternalUploadUrl = externalUploadDestination . getUrl ( ) ; getSftpHost ( currentExternalUploadUrl , externalUploadDestination . getBanner ( ) ) ; disableMultipleFileUploads ( ) ; } else { onFailure ( new org . sagebionetworks . web . client . exceptions . IllegalArgumentException ( ( "Unsupported<seq2seq4repair_space>external<seq2seq4repair_space>upload<seq2seq4repair_space>type:<seq2seq4repair_space>" + ( externalUploadDestination . getUploadType ( ) ) ) ) ) ; } } else if ( ( uploadDestinations . get ( 0 ) ) instanceof ExternalS3UploadDestination ) { ExternalS3UploadDestination externalUploadDestination = ( ( ExternalS3UploadDestination ) ( uploadDestinations . get ( 0 ) ) ) ; storageLocationId = externalUploadDestination . getStorageLocationId ( ) ; currentUploadType = externalUploadDestination . getUploadType ( ) ; String banner = externalUploadDestination . getBanner ( ) ; String bucket = externalUploadDestination . getBucket ( ) ; String key = externalUploadDestination . getBaseKey ( ) ; if ( ! ( DisplayUtils . isDefined ( banner ) ) ) { if ( ( bucket != null ) || ( key != null ) ) banner += "Uploading<seq2seq4repair_space>to<seq2seq4repair_space>an<seq2seq4repair_space>external<seq2seq4repair_space>S3<seq2seq4repair_space>storage:<seq2seq4repair_space>" ; if ( ( externalUploadDestination . getBucket ( ) ) != null ) <START_BUG> bucket = "<seq2seq4repair_space>bucket<seq2seq4repair_space>=<seq2seq4repair_space>" + bucket ; <END_BUG> if ( ( externalUploadDestination . getBaseKey ( ) ) != null ) banner += "<seq2seq4repair_space>key<seq2seq4repair_space>=<seq2seq4repair_space>" + key ; } if ( ! ( DisplayUtils . isDefined ( banner ) ) ) { banner = Uploader . DEFAULT_EXTERNAL_S3_BANNER ; } updateS3UploadBannerView ( banner ) ; } else { onFailure ( new org . sagebionetworks . web . client . exceptions . IllegalArgumentException ( ( "Unsupported<seq2seq4repair_space>upload<seq2seq4repair_space>destination:<seq2seq4repair_space>" + ( uploadDestinations . get ( 0 ) . getClass ( ) . getName ( ) ) ) ) ) ; } } @ Override public void onFailure ( Throwable caught ) { uploadError ( caught . getMessage ( ) , caught ) ; } } ) ; } } public void getSftpHost ( String url , final String banner ) { } public void uploadBasedOnConfiguration ( ) { } public static String getSftpProxyLink ( String realSftpUrl , GlobalApplicationState globalAppState , GWTWrapper gwt ) { } public void uploadToSftpProxy ( final String url ) { } public boolean checkFileAPISupported ( ) { } public void uploadToS3 ( ) { } public UploadType getCurrentUploadType ( ) { } public void setCurrentUploadType ( UploadType currentUploadType ) { } public String getCurrentExternalUploadUrl ( ) { } public void setCurrentExternalUploadUrl ( String currentExternalUploadUrl ) { } public void checkFileSize ( ) throws IllegalArgumentException { } public void checkForExistingFileName ( final String fileName , final Callback callback ) { } private void directUploadStep2 ( String fileName ) { } private void handleCancelledFileUpload ( ) { } public void setFileEntityFileHandle ( String fileHandleId ) { } @ Override public void setExternalFilePath ( String path , String name , Long storageLocationId ) { } public void externalLinkUpdated ( Entity result , Class < ? extends Entity > entityClass ) { } public void updateExternalFileEntity ( String entityId , String path , String name , Long storageLocationId ) { }

Fix:
banner += "<seq2seq4repair_space>bucket<seq2seq4repair_space>=<seq2seq4repair_space>" + bucket ;